The water cycle shows the continuous movement of water within the Earth and atmosphere. It is a complex system that includes many different processes. Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow.

It is also known as the hydrological cycle which refers to the movement of the cycle between above, on, and below of earth's surface in different forms

Stages of Water Cycle

Many processes are involved in the movement of water apart from the major steps given in the above water cycle diagram. Listed below are the different stages of the water cycle.

1. Evaporation

The sun is the ultimate source of energy, and it powers most of the evaporation that occurs on earth. Evaporation generally happens when water molecules at the surface of water bodies become excited and rise into the air. These molecules with the highest kinetic energy accumulate into water vapour clouds. Evaporation usually takes place below the boiling point of water. Another process called evapotranspiration occurs when evaporation occurs through the leaves of plants. This process contributes to a large percentage of water in the atmosphere.

2. Sublimation

Sublimation occurs when snow or ice changes directly into water vapour without becoming water. It usually occurs as a result of dry winds and low humidity. Sublimation can be observed on mountain peaks, where the air pressure is quite low. The low air pressure helps to sublimate the snow into water vapour as less energy is utilised in the process. Another example of sublimation is the phase where fog bellows from dry ice. On Earth, the primary source of sublimation is from the ice sheets covering the poles of the earth.

3. Condensation

The water vapour that accumulates in the atmosphere eventually cools down due to the low temperatures found at high altitudes. These vapours become tiny water and ice droplets, eventually coming together to form clouds.

4. Precipitation

Above 0 degrees centigrade, the vapors will condense into water droplets. However, it cannot condense without dust or other impurities. Hence, water vapours attach itself on to the particle’s surface. When enough droplets merge, it falls out of the clouds and on to the ground below. This process is called precipitation (or rainfall). In particularly cold weather or extremely low air pressure, the water droplets freeze and fall as snow or hail.

5. Infiltration

Rainwater gets absorbed into the ground through the process of infiltration. The level of absorption varies based on the material the water has seeped into. For instance, rocks will retain comparatively less water than soil. Groundwater can either follow streams or rivers. But sometimes, it might just sink deeper, forming aquifers.

6. Runoff

If the water from rainfall does not form aquifers, it follows gravity, often flowing down the sides of mountains and hills; eventually forming rivers. This process is called runoff. In colder regions, icecaps form when the amount of snowfall is faster than the rate of evaporation or sublimation. The biggest icecaps on earth are found at the poles.

All the steps mentioned above occur cyclically with neither a fixed beginning nor an end.